Electric Oven Build Questions

[nickandersonart]

I'm looking to make a more advanced version of my electric Heat Treat oven and have several questions and was hoping some members here could give me some feedback. I was inspired by JT's thread on his oven build with the coils wrapped around ceramic rods inside of quartz tubing - seems like a badass setup

I know that some people consider the extra features here to be a bit overbuilt, but that's ok by me - I consider these builds to be a lot of fun ) Any help is much appreciated!

1) First, I'd also like to do the coils wrapped around ceramic rod inside of the quartz tubing. I plan to use 13 gauge wire. If I'm wrapping coils around a rod of approximately 1/2" diameter, what size quartz tubing should I get and what approximate wall thickness? I see a lot in the range of 1.5-2mm wall thickness. is that enough? I can also go larger on the ceramic rod if needed too.

2) This is more specifically for JT (but if anyone else knows, also helpful) - in your build with the coils suspended from the ceiling, does it heat fairly evenly throughout the oven or does it tend to heat the edge of the blade a lot faster than the rest? Do you think it would it be better to run the coils along the walls or is the ceiling fine? I can get the quartz as long as 1 meter (39 inches).

3) Door design - is it best to have the hinge at the bottom, side, or top of the door? Also, I'm interested in some kind of hands-free system for the door and was thinking of some kind of cantilever system that can be pressed by foot, if it's not too inconvenient. Any ideas? Or better to just use a handle....

4) I'm also very interested in the "Viewing window" that was discussed on here using round quartz plate glass. I've found sizes 20x2mm, 20x3mm, and 15x5mm and am planning on having 2 round plates set apart, mortared into the brick, with an insulated flap on the outside on a hinge. Curious if any of those sizes/thicknesses of quartz glass sound better than the other. Generally, I'd guess that thinner will insulate heat better so perhaps the 2 or 3mm?

I think that's it for now, thank you much for any feedback given!

 

[JTknives]

I do t have aloy of time right now so I will keep it short for now. You ise one of the other, rods or tubes not both. I went with rods and very glad I did. Easy to bend the elament in a zig-zag shape and insert the rids. Infusing tubes you would have to put the tubes over the elament and I don't think it would nearly as easy as the rods where.

My oven seams to heat even but I made sure each rod had the exzact same number of elament loops on it. As to over heating or heating faster. And thin section is going to heat faster then a thick section no mater how it's heated. But this oven does have a lot of radiant heating. But me personally do t think it's a bad thing. Use the extremely fast heating to your advantage by heating the oven and letting it sit and even out and soak. If you have to ramp from room temp then adjust your ramp rate do the coils are not going full blast.

I love the hinge at the bottom, I tossed around tons of ideas and kept coming back to using gravity to keep it closed and open. I would not change one thing about my door system it works really slick.

The Quartz window was just a wild hair idea I had because I had Windows. Come to find out the windows where not Quartz so I'm glad I did not cut out an opening. You will loose radiant heating through the window but if you did 2 windows with an air gap between that should keep the air inside at least insulated from the outside air.

 

[scott.livesey]

here is a guide for building your own furnace http://www.joppaglass.com/elements/dudleys_element_paper_2015.pdf. he goes into specifics on how to mate coils with quartz or ceramic rods and how to mount them in your kiln. the guide also goes into detail on how to make bends, go around corners, and how to terminate and connect the elements to power.
they also sell the elements, rods, and all related items.
scott

 

[Ken H>]

Scott: Thanks for the link. That pdf file has about everything needed to help build an oven. Had I known more, I most likely would have built my oven for the money saving.... AND for the "built it myself" aspect.

Ken H>

 

[nickandersonart]

Hey JT glad to see you pop in to give some feedback on this Ok good to know about the wire over ceramic rod system working nicely. The quartz tubing seems to be quite a bit more expensive, though the fact that they are shielded is still nice.

I am quite interested in the viewing window so I'll probably end up installing one (love being able to see the blade at temp). Glad you found out that those weren't quartz after all haha...would get a nice slumped effect if it turned out to be borosilicate or something like that. I think I'll make it small, two smaller windows of quartz plate glass about 2mm thick. I think 15-20mm diameter would be more than enough.

Regarding the radiant heating of the oven -- I wonder if there would actually be less radiant due to the fact that the profile that is absorbing the radiant heat is only the thin profile of the knife from the top, versus the larger surface area sides of the knife absorbing the radiant heat from the coils on each side. Hm, something to consider...I'm still trying to decide whether to suspend from the top or go along the sides.

Scott I'm looking through the pdf in the link that you sent, wow, this is loaded with all sorts of great information. I'd say that needs to be in the stickies, so much good stuff in it! Now I have a bit of homework to do...

 

[JTknives]

Going in the top for me was much easyer and had to be done to use the gage wire I used. I could not fit that amount of coiled heating elament in the walls. Also the nice thing about the elements on the top is I can use the full width of my oven. I don't have to worry about butting a blade to close to a wall and have it get over heated being closer to the element in the wall.